Poly(rC)-binding proteins (PCBPs) are cellular RNA-binding proteins, characterized by their triple KH structure and by their poly(C)-binding specificity. The 3 KH domains are not only involved in nucleic acid binding but also mediate protein-protein interactions within the RNP complexes. It binds specifically to polypyrimidine tracts within the 3' UTR of target mRNAs through KH domains. PCBPs are expressed as 4 isoforms in cells. PCBP1 and PCBP2 are predominantly expressed in the nucleus and can shuttle from the nucleus to the cytoplasm, while PCBP3 and PCBP4 are expressed to a less extent in the cytoplasm. The most characterized gene regulated by PCBP1 and PCBP2 is the -globin gene, and the accumulated -globin mRNA is known to account for approximately 95% of total cellular mRNA during terminal erythroid differentiation. Specific binding of PCBPs to 3′ UTR of mRNA is associated with the stabilization of -globin mRNA. Microarray analysis of human mRNAs present in a specific subset of PCBP2-RNP complexes also showed a potential involvement of PCBP2 in transcription factor expression via association with their mRNA; further, the enrichment of PCBP2 mRNA in PCBP2-RNP complexes suggested that PCBP2 expression may be subject to posttranscriptional autoregulation.